Prevents smearing dark spots on light-colored markers

I decided to switch all my caps (on the ~50+ markers I own) to transparent ones, so that the small smears on the inside are visible and I can then easily match each cap to its corresponding marker. In the past, with the black opaque caps, a recurring problem is that you accidentally put a "black" cap on a red marker, and as you are manipulating the cap, the black residue smears onto the red nib, resulting in ugly lines.

I would recommend that Neuland switch to transparent caps entirely for this very reason.